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(quite/very) (un)likely that X is the author of the email.”
However, as Philip Rose argues convincingly, expressing an
opinion in this form is tantamount to expressing an opinion on
the likelihood of the accused being guilty, which is the exclusive
role of the judges of fact.^10 All that a linguist can comment on is
the degree of similarity or difference between linguistic choices
in the questioned and the known texts. Rose supports his
argument by pointing out that no expert can make an estimate of
the likelihood of guilt or innocence on the basis of the linguistic
evidence alone; only those with access to all the available
evidence can assess the value of each piece of it.^11 For this
reason, I prefer to approach questions of authorship attribution
as a two-stage process, asking first if the choices in the
questioned document are compatible with choices made by the
potential authors in their known documents. If the choices are
not compatible, no further analysis is undertaken. Then, as a
second stage for those candidate author(s) for whom the choices
are indeed compatible, one comments on how distinctive the
particular linguistic choices are, on a five-point scale from not
distinctive to exceptionally distinctive.
II. THE BRIEF
I was asked to express an opinion on the likely authorship of
a questioned email sent from the email account of a Mr. Stephen
Goggin to a Mr. Denis Juola at 16.30 on July 23, 2004. I was
briefed that, given the timing and content of the email, in
particular the knowledge of and explicit reference to an earlier
phone call to Mr. Juola timed at 14.50, only a small number of
people—Mr. Goggin; Mr. Tim Widdowson, the CEO; Mr. John
Shuy, the Finance Director of MaxiSoft; and possibly their PA,
Ms. Janet Gavalda—could have been in a position to author and
type the email. I was asked to proceed on the assumption that,
although the email was sent from Mr. Goggin’s e-account, it
may not have been physically typed on his computer, because
(^10) PHILIP ROSE, FORENSIC SPEAKER IDENTIFICATION 76 (James Robinson
ed., 2002).
(^11) Id. at 68.